1. Field of the Invention
The invention relates to a straddle-type vehicle.
2. Description of Related Art
Conventionally, a vehicle comprising a transmission with plural transmission gears is known. A clutch is connected and disconnected in a change gear operation of the transmission. A clutch operation member, such as a clutch lever, for driver operation of the clutch and a change gear operation member, such as a shift pedal, for operating the transmission are usually provided.
The clutch operation member and the clutch, and the change gear operation member and the transmission, are often connected through a mechanical power transmitting mechanism such as a link, a rod and a wire. Manipulating force of a driver is transmitted to the clutch and the transmission via the power transmitting mechanism.
Use of an actuator such as an electric motor to connect and disconnect the clutch or change transmission gears has recently been attempted. For example, an actuator to generate an assist force to reduce a load of a driver operating the clutch has been proposed.
JP-A-2000-205396 discloses a sensor for detecting depression of a clutch pedal in an automobile and an actuator for changing the engaging force of the clutch based on a detection signal from the sensor.
JP-A-2004-76897 discloses a motorcycle including a wire (a mechanical power transmitting mechanism) for connecting a clutch lever and a clutch and a power transmitting mechanism for connecting a shift pedal and a transmission. An actuator for connecting and disconnecting the clutch and an actuator for changing transmission gears are separately provided. Clutch and change gear operations can be optionally switched between manual and automatic operations.
However, these prior art actuators only generate assist force for reducing the manipulating force of the clutch and do not change a characteristic of the clutch.
Further, the vehicle of JP-A-2000-205396 is an automobile and the clutch operation member is a stepping-type pedal. A driver cannot carry out a sensitive operation since the pedal is operated by means of a foot. In a straddle-type vehicle such as a motorcycle, by contrast, a driver tends to attach more importance to manipulating performance and sometimes carries out a subtle operation to quickly or substantially change the movement of the motorcycle.
The vehicle of JP-A-2004-76897 provides switching between a manual mode and an automatic mode. This enables secure freedom of drive or easy operation to be achieved, based on the assumption that a driver attaching importance to manipulating performance (freedom of drive) selects the manual mode while a driver preferring to avoid trouble or difficulty in operation (in other words, a driver preferring easy operation) selects the automatic mode. However, fixed easiness of operation and fixed freedom of drive cannot be simultaneously achieved since the manual and automatic modes are alternatively selected. Thus, operation remains troublesome in manual mode while freedom of drive is lost in automatic mode.